Grammarly’s free spelling and grammar checker ensures that everything you type is easy to read, effective, and mistake-free. As you type, Grammarly underlines spelling mistakes and grammatical errors and helps you fix them on the fly.

Translate selected word or phrase over translate.yandex.ru from any lang to Russian (or from Russian to English) - result in context menu (right click) and in popup. Minimum and fast. Not affect DOM. Unofficial extension - works by using API.

Translate entire web page or selected text using google translateThere are many translators on Firefox. There are two features they're not supported:1.HTTPS pages2.Page loginedThis addon can translate all pages you can open in firefox